Abstract

Contracting 3D Printed Microtissues: Solid and Fluid Instabilities

Thomas Angelini, Associate Professor, Department of Mechanical and Aerospace Engineering, University of Florida

Living cells are often dispersed in extracellular matrix (ECM) gels like
collagen and Matrigel as minimal tissue models. Generally, large-scale
contraction of these constructs is observed, in which the degree of
contraction and compaction of the entire system correlates with cell
density and ECM concentration. The freedom to perform diverse mechanical
experiments on these contracting constructs is limited by the
challenges of handling and supporting these delicate samples. Here, we
present a method to create simple cell-ECM constructs that can be
manipulated with significantly reduced experimental limitations. We 3D
print mixtures of cells and ECM (collagen-I) into a 3D growth medium
made from jammed microgels. With this approach, we design microtissues
with controlled dimensions, composition, and material properties. We
also control the elastic modulus and yield stress of the jammed microgel
medium that envelops these microtissues. Similar to well-established
bulk contraction assays, our 3D printed tissues contract. By contrast,
the ability to create high aspect ratio objects with controlled
composition and boundary conditions allows us to drive these
microtissues into different regimes of physical instability. For
example, a contracting tissue can be made to buckle as a whole or break
up into droplets, depending on composition, size, and shape. These new
instabilities may be employed in tissue engineering applications to
anticipate the physical evolution of tissue constructs under the forces
generated by the cells within.